Refrigerant

ABSTRACT

An object of the present invention is to provide a refrigerant in which an odorant is added, the odorant being compatible with refrigerants and refrigerating device oils, and having no reactivity with refrigerating device oils and materials forming refrigerating circuits, and to provide a refrigerating device in which the refrigerant is circulated in the refrigerating circuit. 
     A refrigerant whose main component is a hydrocarbon having 1 to 4 carbon atoms, or a flammable hydrocarbon fluoride obtained when one or more hydrogen atoms of the hydrocarbon is substituted by fluorine atoms, the refrigerant containing a tetrahydrothiophene as an odorant, and a refrigerating device in which the refrigerant is circulated are provided.

This is a divisional of U.S. application Ser. No. 09/908,760 filed Jul.19, 2001, which claims priority based on Japanese Patent Application No.2000-227678 filed Jul. 27, 2000, and the complete disclosure of which ishereby incorporated by this reference thereto.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a refrigerant and a refrigeratingdevice, and in particular, to a flammable refrigerant in which anodorant is incorporated and a refrigerating device which utilizes theflammable refrigerant.

2. Description of the Related Art

Refrigerators and refrigerating devices for automatic vending machinesand showcases have usually used, as a conventional refrigerant,chlorofluorocarbon refrigerants such as dichlorodifluoromethane(CFC-12), or hydrochlorofluorocarbon refrigerants such aschlorodifluoromethane (HCFC-12). When these refrigerants are releasedinto the atmosphere and reach the ozone layer above the earth, theproblem of destruction of the ozone layer arises. Thus, use ofchlorofluorocarbon flon and hydrochlorofluorocarbon flon, which arerefrigerants which have been used until now in refrigerating devices,has been prohibited or restricted.

As a result, hydrofluorocarbon refrigerants such as CH₂FCF₃ (HFC-134a)have been used as a substitute flon of the above refrigerants. However,even with such HFC refrigerants, a problem arises in that the effectthereof on global warming, which is another global environmental issue,is near the same level as that of the conventional HCFC-22 (CHCIF₂)which is an HCFC refrigerant.

To solve such problems, hydrocarbon (HC) refrigerants such as propaneand isobutane have recently been used as refrigerants for refrigeratingdevices. However, because the HC refrigerants are flammable, there isthe possibility of spontaneous ignition or explosion when theserefrigerants leak from a refrigerating circuit. Particularly, in thecase of home refrigerators, since many heat sources often disposed nearthe home refrigerator, leakage of the flammable refrigerant may cause amajor accident.

In view of the aforementioned facts, for refrigerating devices whichutilize flammable gas refrigerants, it has been proposed to add odorantsto refrigerants so that the leakage of the gas refrigerants can bedetected. For example, Japanese Patent Application Laid-Open (JP-A) No.8-14675 discloses addition of methylmercaptan, as an odorant made ofsulfur-containing organic substance, to the HC refrigerant. However,methylmercaptan has high reactivity with copper, which is a materialused in the refrigerating circuit, and changes (corrodes) the coppersurface, which results in a shortened life of the copper. In addition,methylmercaptan also has high reactivity with refrigerating device oils.When it reacts with the refrigerating device oil, an insoluble reactionproduct will be generated in the refrigerant or in the refrigeratingdevice oil, which insoluble reaction product may cause clogging of acapillary tube or the like in the refrigerating circuit after operationfor a long period of time.

JP-A No. 8-245952 discloses that, in addition to mercaptane (methylmercaptane, ethylmercaptane), dimethyl sulfide is added, as an odorant,to a flammable HFC refrigerant. However, dimethyl sulfide does not havean extremely strong offensive smell (it only has an onion-like smell),so that dimethyl sulfide alone does not sufficiently function as anodorant for the flammable refrigerant. As a result, it is generally usedin combination with other odorants such as mercaptanes.

Therefore, a flammable refrigerant incorporating an odorant whichodorant has no reactivity with copper, a material of the refrigeratingcircuit, or refrigerating device oils has not been developed.

An odorant is generally required to have such characteristics that ithas an abnormal smell, is stable as a chemical substance, is non-toxicand harmless to humans, and the like. In addition, particularcharacteristics are required depending on materials to which the odorantis added. Therefore, a substance known as an odorant can not always beused as the odorant for other materials.

For example, tetrahydrothiophene (THT) has already been used as anodorant in combustion gases such as town gas (“Perfume” No. 146, June1985). In addition to the above characteristics generally required forodorants, the following particular characteristics are necessary forodorants used in combustion gases: it burns safely and is odorless andharmless after combustion takes place, the odor is held in the gas so asnot to be absorbed by gas pipes and meters, and the like. Because addingTHT to combustion gases and adding THT in refrigerants for refrigeratingcircuit have been considered as two different things, use of THT inrefrigerants has not been examined.

SUMMARY OF THE INVENTION

In view of the aforementioned facts, an object of the present inventionis to provide a refrigerant in which an odorant is added, the odorantbeing compatible with refrigerants and refrigerating device oils, andhaving no reactivity with refrigerating device oils and materials usedfor refrigerating circuits, and to provide a refrigerating device inwhich the refrigerant is circulated in the refrigerating circuit.

The following refrigerants and refrigerating devices of the presentinvention are provided in order to achieve the above-described object.

A first aspect of the present invention is a refrigerant the maincomponent of which is a hydrocarbon having 1 to 4 carbon atoms, or aflammable hydrocarbon fluoride derived by substituting one or morehydrogen atoms of the hydrocarbon with fluorine atoms, the refrigerantincluding a tetrahydrothiophene as an odorant.

A second aspect of the present invention is the refrigerant in which theamount of the odorant is in the range of 10 wt ppm to 0.5 wt %.

A third aspect of the present invention is the refrigerant in whichpurity of the hydrocarbon or the flammable hydrocarbon fluoride is atleast 99.0 vol %, the content of unsaturated hydrocarbon is no more than0.01 wt %, and the entire sulfur content is no more than 0.1 wt ppm.

A fourth aspect of the present invention is a refrigerating device inwhich the refrigerant of the first aspect of the invention is circulatedin a refrigerating circuit in which a compressor, a heat releasingdevice, an expansion mechanism, and an evaporator are included.

A fifth aspect of the present invention is the refrigerating device inwhich a refrigerating device oil used in the compressor has a viscosityat 40° C. of 5 to 300 cSt.

A sixth aspect of the present invention is the refrigerating device inwhich the refrigerating device oil includes a metal inactivating agent.

A seventh aspect of the present invention is the refrigerating device inwhich the refrigerating device oil includes one or more additivesselected from the group consisting of moisture- and/or acid trappingagents, antioxidants, and extreme pressure additives.

An eighth aspect of the present invention is the refrigerating device inwhich residual oxygen in the refrigerating circuit is no more than 0.1vol % of an internal capacity of the refrigerating circuit, and aresidual moisture content in the refrigerating circuit is no more than500 wt ppm with respect to a total of the refrigerant and therefrigerating device oil.

A ninth aspect of the present invention is the refrigerating device inwhich the refrigerating circuit is made of copper or copper alloy.

A tenth aspect of the present invention is the refrigerating device inwhich the refrigerating circuit further includes a drying device.

An eleventh aspect of the present invention is the refrigerating devicein which the drying device contains a synthetic zeolite whose effectivediameter falls in the range of 3 to 6 Å.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic view illustrating one example of a refrigeratingcircuit in the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The main component of the refrigerant of the present invention is ahydrocarbon having 1 to 4 carbon atoms, or a flammable hydrocarbonfluoride in which some of the hydrogen atoms of hydrocarbon aresubstituted by fluorine atoms. These refrigerants are known as flammablerefrigerants. Examples of the hydrocarbon having 1 to 4 carbon atomsinclude propane, isobutane, or the like. The flammable hydrocarbonfluoride is the hydrocarbon fluoride in which a part of hydrocarbonhaving 1 to 3 carbon atoms is substituted by fluorine atoms, andexamples thereof include: difluoromethane, difluoroethane (1,1- or1.2-difluoroethane), trifluoroethane (1,1,1- or 1,1,2-trifluoroethane),tetrafluoroethane (1,1,1,2- or 1,1,2,2-tetrafluoroethane),pentafluoroethane, pentafluoropropane (1,1,2,2,3- or1,1,1,3,3-pentafluoropropane, etc.), hexafluoropropane (1,1,2,2,3,3- or1,1,1,2,3,3-hexafluoropropane, etc.), heptafluoropropane (1,1,1,2,2,3,3-or 1,1,1,2,3,3,3-heptafluoropropane, etc.), or the like. The purity ofthe hydrocarbon is preferably 99.0 vol % or higher, the total amount ofunsaturated hydrocarbon contained therein is preferably 0.01 wt % orless, and the entire sulfur content contained therein is preferably 0.1wt ppm or less. If the purity of the hydrocarbon or the flammablehydrocarbon fluoride is less than 99.0 vol %, there are cases in whichadverse effects due to the impurities may arise. If the total amount ofunsaturated hydrocarbon exceeds 0.01 wt %, unsaturated hydrocarbonreacts with the refrigerating device oil in the refrigerating circuitand with materials forming the refrigerating circuit. As a result,deterioration of the refrigerating circuit tends to occur. Further, ifthe entire content of sulfur exceeds 0.1 wt ppm, the reaction with thecopper forming the pipes will exceed allowable limits, which is notpreferable.

Next, the odorant used in the present invention will be described. Anodorant is generally required to have such characteristics that it hasan abnormal offensive smell, is stable as a chemical substance, isnon-toxic and harmless to humans, and the like. In addition to the abovecharacteristics, the following particular characteristics are requiredfor the odorant particularly for use in refrigerants: it does not reactwith materials, particularly copper, forming the refrigerating circuit;it is compatible with refrigerants; and it is compatible with, but doesnot react with the refrigerating device oil which is mixed with therefrigerant and together circulates in the refrigerating circuit. Otherthan these characteristics, the odorant must have an appropriate boilingpoint and solidifying point. If the boiling point is too high, theodorant hardly vaporizes and does not function well as an odorant. Ifthe solidifying point is too high, the odorant solidifies in therefrigerant, which may cause clogging of the refrigerating circuit.

The odorant used in the refrigerant of the present invention istetrahydrothiophene (hereinafter, sometimes referred to as THT). THT isa liquid substance at ordinary temperature and has a unique offensivesmell (a smell like that of coal gas), a boiling point of 122° C., and asolidifying point of −96° C. Accordingly, THT sufficiently functions asan odorant in the case of leakage of the refrigerant, and, because THTdoes not solidify when used in refrigerants, problems such as cloggingof the refrigerating circuit can be avoided. In addition, THT has goodcompatibility with above-described hydrocarbon, flammable hydrocarbonfluoride, and later-described refrigerating device oils. As an importantcharacteristics, THT does not react with materials, especially copperand copper alloy, which form the refrigerating circuit. Therefore, THTdoes not cause corrosion of copper pipes, heat exchangers, or the like.In addition, since THT does not react with refrigerating device oils,clogging of the refrigerating circuit due to insoluble reaction productswill not occur even after operation for a long period of time.

The added amount of the odorant in the refrigerant is preferably 10 wtppm to 0.5 wt %. When less than 10 wt ppm is used, it becomes difficultto detect leakage of the refrigerant. If even more than 0.5 wt % isadded, the odor becomes stronger than necessary, and, as a result,handling of the odorant becomes difficult when the odorant is filled inthe refrigerant circuit and recovered therefrom. Therefore, theaforementioned range is preferable.

The present invention also relates to a refrigerating device whichcirculates a refrigerant through a refrigerating circuit in which acompressor, a heat releasing device, an expansion mechanism, and anevaporator are included.

FIG. 1 is a schematic view for explaining one example of a coolingcircuit in the refrigerating device of the present invention. In FIG. 1,reference numeral 100 represents a compressor, 120 denotes a heatreleasing device, 140 represents an expansion mechanism (a capillarytube), 160 denotes a gas cooler, 180 is a four-way valve, and 200represents a drying device. The arrows denote the direction in which therefrigerant flows. The solid line arrows illustrate the flow of therefrigerant when the ordinary cooling is carried out, and the dashedarrows indicate the flow of the refrigerant when the defrosting iscarried out. In FIG. 1, an example is illustrated in which the dryingdevice is provided between the expansion mechanism 140 and the heatreleasing device 120. However, the drying device does not have to beprovided at this position, and may be provided at another low-pressureposition.

For example, in a case in which the interior of a room is to be cooled,the refrigerant gas, which is under high temperature and high pressureand is compressed by the compressor 100, passes through the four-wayvalve 180, such that heat is released at the heat releasing device 120and the refrigerant is cooled so as to become a low-temperature,high-pressure refrigerant liquid. The pressure of the refrigerant liquidis lowered by the expansion mechanism 140 (e.g., a capillary pipe, atemperature-type expansion valve, or the like), so as to become alow-temperature, low-pressure liquid containing a slight amount of gas.This liquid reaches the gas cooler 160, obtains heat from the air withinthe room, evaporates, passes through the four way valve 180, and reachesthe compressor 100 to cool the interior of the room. When the gas cooleris to be defrosted, the flow of the refrigerant is changed to theopposite direction by the four way valve 180, and the oppositeoperations are carried out so as to defrost. When an exterior heatchanger is used as the heat releasing device while an interior heatexchanger is used as the gas cooler, the present invention can also beapplied to a heating and cooling type air conditioner.

The refrigerating device oil is a lubricating oil sealed within thecompressor. A mixture of a refrigerant and a small amount of therefrigerating device oil circulates through the entire refrigeratingcircuit. Therefore, the odorant incorporated in the refrigerant iscaused to be in contact with the refrigerating device oil. Accordingly,the odorant is required to be compatible with, and have no reactivitywith the refrigerating device oil.

Accordingly, the low-temperature characteristic and the miscibility withrespect to the refrigerant, of the refrigerating device oil areimportant for the performance of the cooling system. The mixture of therefrigerant and the refrigerating device oil must be stable (e.g., mustbe resistant to hydrolysis) at operating temperatures of therefrigerating device. Further, the mixture must not be harmful to (e.g.,must not corrode or lower the insulation of) the compressor as well asthe other materials used in the refrigerating circuit. Further, aportion of the refrigerating device oil is mixed in with the compressedrefrigerant gas, is circulated together with the refrigerant in therefrigerating circuit of the refrigerating device, and flows into theevaporator through an expansion mechanism such a capillary pipe or anexpansion valve. At the low temperature portions in the refrigeratingcircuit, the refrigerating device oil which moves from the compressorloses its fluidity, and the refrigerating device oil tends to remainthereat. If the refrigerating device oil does not return to thecompressor from the evaporator, the level of the oil on the surfaces inthe compressor will fall, and this may cause heat damage (seizing due toincreased temperature).

The viscosity of the refrigerating oil at 40° C. is preferably 5 to 300cSt. When the viscosity is greater than 300 cSt, the fluidity isinsufficient, and the fluidity tends to be lost, especially at lowtemperatures. Further, if the viscosity is less than 5 cSt, insufficientoil film strength at the lubricating surfaces and an insufficientsealing effect at the compressor mechanism tend to occur.

Further, the volume specific resistivity of the refrigerating device oilat the refrigerating device of the present invention is preferably 10¹⁰Ω·cm or more.

General petroleum oils, ether synthetic oils, ester synthetic oils,fluorine synthetic oils and the like can be used as the refrigeratingdevice oil at the refrigerating device of the present invention.Examples of petroleum oils are paraffin oils and naphthene oils.Further, polyvinylethers and polyalkylene glycols may be used as theether synthetic oils. Examples of the ester synthetic oils are polyolester oil, carbonate ester, and the like.

A polyester from a polyvalent alcohol and a polyvalent carboxylic acidis preferably used as the ester synthetic oil. Among these, polyesteroils synthesized from a fatty acid and a polyvalent alcohol selectedfrom pentaerithritol (PET), trimethylolpropane, (TMP), andneopentylglycol (NPG) are preferably used.

In the case in which hydrocarbon is used as the refrigerant, petroleumoils are preferably used as the refrigerating device oil while in thecase in which a flammable hydrocarbon fluoride is used as therefrigerant, ether synthetic oils such as polyvinylether are preferablyused as the refrigerating device oils. Further, a mixture of one or moretypes of refrigerating device oils may be used as the refrigeratingdevice oil.

Additives such as defoaming agents, antioxidants, moisture-and/or acidtrapping agents, extreme pressure additives or antiabrasion improvingagents, and metal inactivating agents, especially copper inactivatingagents, may be added to the refrigerating device oil. It is preferableto use additives to prevent alterations (decomposition, oxidation,formation of sludge, and the like) of the refrigerating device oil andalterations (corrosion) of the materials forming the refrigeratingcircuit. In addition, heat-resistance improving agents, corrosionpreventing agents, rust-preventing agents and the like may be suitablyadded.

The additives to the refrigerating device oil do not only haveparticular effects on the refrigerating device oil itself, but alsoconsequently have certain effects on the sliding portions of thecompressor, the insulating materials, and the pipe metals. One or moretypes of these additives may be used. Further, as described above,because a mixture of the refrigerant and a small amount of refrigeratingdevice oil is circulated through the refrigerating circuit, therefrigerating device oil, to which the above additives are added, mustnot exert any harmful effects on the materials used in the refrigeratingcircuit.

As the defoaming agent, dimethylpolysiloxane oil, trifluoropropylmethylsilicone oil, phenylmethyl silicone oil and the like are preferablyused.

The added amount of the defoaming agent is preferably 1 to 50 wt ppmwith respect to the refrigerating device oil. When less than 1 wt ppm isused, the effects of the defoaming agent are insufficient. If more than50 wt ppm is added, the effects as a defoaming agent do not increase.Therefore, the aforementioned range is preferable.

By adding the defoaming agent, when the air within the refrigerantcompressor and the circuit is removed before refrigerant sealing, theamount of foam generated from the refrigerating device oil is decreased,and entry of foam into the deaerating device can be prevented. Inaddition, foaming occurring at the time when the air dissolved in therefrigerating device oil is removed can be prevented.

The antioxidants may be hindered phenol antioxidants such as ditertiarybutylparacresol (DBPC), 2,6-di-t-butyl-4-methylphenol, 4,4′-methylenebis(2,6-di-butylphenol), 2,2′-thiobis(4-methyl-6-t-butylphenol) or thelike; amine antioxidants such as P,P′-dioctyldiphenylamine,3,7-dioctylphenothiazine, phenyl-α-naphthylamine, di(alkylphenyl)amine(wherein the alkyl group has from 4 to 20 carbon atoms),phenyl-α-naphthylamine, alkyldiphenylamine (wherein the alkyl group hasfrom 4 to 20 carbon atoms), N-nitrosodiphenylamine, phenothiazine,N,N′-dinaphthyl-p-phenylenediamine, acridine, N-methylphenothiazine,N-ethylphenothiazine, dipyridylamine, diphenylamine, phenolamine,2,6-di-t-butyl-α-dimethylaminoparacresol and the like; and sulfurantioxidants such as alkyl disulfides or the like. Among these, DBPC isparticularly preferably used. The added amount of the antioxidant ispreferably 0.1 to 0.5 wt % with respect to the refrigerating device oil.When the amount is less than 0.1 wt %, the effects as an antioxidant areinsufficient. When an antioxidant is added in an amount exceeding 0.5 wt%, additional effects are not achieved. Thus, the aforementioned rangeis preferable.

The residual oxygen in the refrigerating circuit is preferably 0.1 vol %or less with respect to the internal volume of the refrigeratingcircuit.

It is preferable to add a moisture- and/or acid trapping agent to therefrigerating device oil. Water and acidic substances cause corrosion ofthe metals used in the compressor. In addition, water and acidicsubstances cause hydrolysis when an ester oil is used as therefrigerating device oil, and this frees the fatty acid components. Thisleads to the possibility of the refrigerating circuit being closed offdue to the generation of corrosion or metallic soaps, and of hydrolysisof the ester insulating materials.

Epoxy compounds, carbodiimide compounds, and the like may be used as themoisture- and/or acid trapping agent. The epoxy compounds may trapradicals. Examples of the epoxy compounds are glycidyl esters, glycidylethers, and the like. For example, a phenylglycidyl ether type epoxycompound or an epoxydated fatty acid monoester or the like may be used.Phenylglycidyl ether or alkylphenylglycidyl ether, for example, may beused. The alkylphenylglycidyl ether has 1 to 3 alkyl groups having 1 to13 carbon atoms. Examples of the epoxidated fatty acid monoesters areesters of an epoxidated fatty acid having 12 to 20 carbon atoms, and analcohol having 1 to 8 carbon atoms or a phenol or alkylphenol. Inparticular, esters of butyl, hexyl, benzyl, cyclohexyl, methoxyethyl,octyl, phenyl or the like of epoxystearic acid are preferable. The addedamount of the moisture- and/or acid-trapping agent is preferably 0.1 to0.5 wt % with respect to the refrigerating device oil. When the amountis less than 0.1 wt %, the effect as a trapping agent is insufficient.When the amount is greater than 0.5 wt %, polymers tend to be generated.Thus, the above range is preferable. It is preferable that the residualmoisture is 500 wt ppm or less, and more preferably 200 wt ppm or less,with respect to the total of the refrigerant and the refrigeratingdevice oil. By using a moisture-trapping agent such as those mentionedabove, the equilibrium moisture content within the refrigeratingcircuit, which content is expressed by the following formula, can bekept to 200 wt ppm or less in the initial stags of operation of therefrigerating device. When the moisture contents exceeds 500 wt ppm,icing tends to occur within the capillary pipes. Further, hydrolysis,which is caused when a polyester oil is used as the refrigerating deviceoil, and the generation of metal soap sludge which accompanies suchhydrolysis, can be suppressed.

[(residual moisture amount within refrigerating circuit)/(amount of oilfilled+amount of refrigerant filled)]×10⁶ wt ppm  Formula 1

For example, a tertiary phosphate phosphorus compound which is thermallystable, such as triphenylphosphate (TPP) or tricresylphosphate (TCP), orthe like may be used as the extreme pressure additive. Among these, TCPis particularly preferably used.

The added amount of the extreme pressure additive is preferably 0.1 to 2wt % with respect to the refrigerating device oil. If the amount is lessthan 0.1 wt %, the effects as an extreme pressure additive areinsufficient. If the added amount exceeds 2 wt %, no additional effectsare exhibited, and therefore, the above range is preferable.

Examples of the metal (particularly, copper) inactivating agent arebenzotriazole (BTA), triazole, triazole derivatives, thiadiazole,thiadiazole derivatives, dithiocarbamate, alizarin, qunizarin, and thelike. Among these, BTA is preferably used.

The added amount of the metal inactivating agent is preferably 1 to 100wt ppm with respect to the refrigerating device oil. If the amount isless than 1 wt ppm, the effects as a metal inactivating agent areinsufficient. If the added amount exceeds 100 wt ppm, no additionaleffects are obtained. Therefore, the above range is preferable.

The drying agent is preferably a synthetic zeolite or the like. Amongsynthetic zeolites, sodium A type synthetic zeolite and potassium A typesynthetic zeolite are preferable. Further, in order for the zeoliteparticles to effectively trap the moisture within the refrigeratingcircuit, it is preferable for the effective diameter thereof to fall inthe range of 3 to 6 Å.

The drying device used in the refrigerating device may be one in whichthe drying agent is accommodated within a container, and the containeris connected by a pipe to the refrigerating circuit.

Hereinafter, the present invention will be described specifically by anExample. However, it is to be noted that the present invention is notlimited to this example.

EXAMPLE 1

A refrigerating device was assembled by using materials such as thefollowing, by using the refrigerating circuit shown in FIG. 1.

refrigerant: isobutane (purity 99.7 vol %, 0.001 wt % of unsaturatedhydrocarbon, 0.05 wt ppm of sulfur)

odorant: tetrahydrothiophene (0.1 wt % with respect to the refrigerant)

refrigerating device oil: paraffin oil

viscosity (40° C.):15 cSt

volume specific resistivity: 10¹⁵ Ω·cm

refrigerating device oil aditives (added amount is wt % with respect torefrigerating device oil)

defoaming agent: silicone defoaming agent (10 ppm)

antioxidant: DBPC (0.3%)

moisture- and/or acid-trapping agent: epoxy compound (0.25%)

extreme pressure additive: TCP (1%)

copper inactivating agent: BTA (5 ppm)

drying agent: synthetic zeolite (effective diameter: 3 Å)

The above refrigerant had a unique smell (a smell like that of coalgas), and it was easy to detect the leakage of the refrigerant even in asmall amount. Further, after operation of the above refrigerating devicefor 2000 hours, the state of the inner surface of the copper pipe of therefrigerating circuit and the inner surface of the capillary tube wereinspected, and were found to have no corrosion.

As described above, in the refrigerant of the present invention, byusing tetrahydrothiophene as the odorant and due to its smell, it iseasy to detect the leakage of the refrigerant from the refrigeratingdevice. In addition, the odorant has good reactivity with therefrigerant and the refrigerating device oil. In particular, therefrigerant does not react with copper forming the refrigeratingcircuit, and causes no corrosion at the surface of the copper. Further,the refrigerant has no reactivity with the refrigerating device oil.Therefore, clogging of the refrigerating circuit due to insolublereaction products will not occur even after operation for a long periodof time.

What is claimed is:
 1. A refrigerant comprising: (i) a hydrocarbonhaving 1 to 4 carbon atoms, or a flammable hydrocarbon fluoride having astructure derived by fluorine atoms for one or more hydrogen atoms ofsaid hydrocarbon, as a main component, and (ii) a tetrahydrothiophene asan odorant, wherein purity of the hydrocarbon or the flammablehydrocarbon fluoride is at least 99.0 vol %, the content of unsaturatedhydrocarbon is no more than 0.01 wt %, and the entire sulfur content isno more than 0.1 wt ppm.
 2. A refrigerant comprising: (i) a hydrocarbonhaving 1 to 4 carbon atoms, or a flammable hydrocarbon fluoride having astructure derived by substituting fluorine atoms for one or morehydrogen atoms of said hydrocarbon, as a main component, and (ii) atetrahydrothiophene as an odorant, wherein the amount of the odorant isin the range of 10 wt ppm to 0.5%, purity of the hydrocarbon or theflammable hydrocarbon fluoride is at least 99.0 vol %, the content ofunsaturated hydrocarbon is no more than 0.01 wt %, and the entire sulfurcontent is no more than 0.1 wt ppm.